This invention relates generally to renewable power generation and more specifically to detection of islanding for a power generation facility connected to a grid. The system and method are particularly applicable to solar, wind, and other renewable power generation systems.
Renewable energy sources such as solar energy sources, wind energy sources, and hydrokinetic energy sources have increasingly penetrated the power generation space in recent years. One challenge in feeding the power generated by renewable energy sources to the grid is islanding, which refers to a condition in which a renewable energy source continues to feed power even though the electric utility (grid) is no longer coupled to the energy source. The detection of an islanding condition is important for safety and grid stability.
A number of passive and active methods for islanding detection have been proposed. Many of these methods either have longer than desirable detection times or fail to detect all islanding conditions.
In one example of an active method of islanding detection using reactive power, a small amount of reactive power is continuously fed by the power conversion system and causes the power conversion system to be shut down upon an islanding condition. In this example, injecting a higher amount of reactive power results in shorter detection period with higher power conversion losses, whereas injecting a lower amount of reactive power results in lower losses but a longer detection period. Hence low losses and short detection time requirements appear contradictory.
Accordingly, a technique is needed to detect an islanding condition with reasonable speed and acceptable power.